This invention relates to an image recording apparatus, and more particularly to a light beam multiformat camera used in the field of medical treatment to record an the obtained by output image such as CT (computed tomography), DR (digital radiology), NMR (nuclear magnetic resonance) or an ultrasonic wave on a recording sheet by a light beam while dividing the image into a plurality of images.
2. Description of the Prior Art
For the image recording of a diagnostic apparatus or an like using CT, DR, NMR or ultrasonic wave, use has often been made of a camera for photographing an output CRT image on a recording medium such as a film through an optical system, particularly a multiformat camera for divisionally recording a plurality of picture planes P on a recording sheet S as shown in FIG. 1 of the accompanying drawings. However, it has the following disadvantages:
(i) Since an image is first projected on a CRT and then is photographed on a recording sheet through an optical system, the sharpness of the image is impaired;
(ii) The CRT image has a great reduction in quantity of marginal light; and
(iii) The CRT multi-image is narrow in dynamic range.
These disadvantages arise from the intervention of the CRT and recently, to eliminate such disadvantages, a system has been proposed in which an image in the form of an electrical signal is directly recorded on a recording sheet by a light beam. Generally, a light beam image recording apparatus is known which has beam generating means and beam modulating means and in which, as shown in FIG. 2 of the accompanying drawings, major scanning (the direction of arrow X) is effected by a light beam scanning optical system 27 and subsidiary scanning (the direction of arrow Y) is effected with a recording sheet 2 along a drum 13 which makes one full rotation in the direction of arrow Z. A detailed side view of such apparatus is shown in FIG. 4 of the accompanying drawings. It would come to mind to use this apparatus to divisionally record a plurality of images P on a recording sheet 2 as shown in FIG. 3 of the accompanying drawings, that is, to endow the apparatus with the function as a light beam multiformat camera.
Now, in the conventional apparatus shown in FIG. 4, a recording sheet taken out from a supply magazine 202 by a taking-out mechanism 203 and supplied to a drum 201 is fed to the drum 201 via is recorded by a laser beam L while being fed by urge rollers 206a, 206b and is discharged, for example, into a container magazine by discharging rollers 208a, 208b via a guide plate 207. During the image recording, the recording sheet S is fed along the drum 201 only by the driving of the drum 201 in a state in which the recording sheet is completely separate from the rollers 204a, 204b, 208a, 208b forward and rearward of the drum 201, that is, a state in which any other force than gravity is not applied to the recording sheet. In this method, however, the spacings between the drum 201 and the rollers 204a, 204b, 208a, 208b must be equal to at least the length of the recording sheet S in the feeding direction, and this leads to a disadvantage that the recording unit becomes bulky.
Further, in the above-described conventional apparatus, all information is recorded on the recording sheet by one subsidiary scanning, and this leads to the following disadvantages:
(i) Since a plurality of types of image information must be stored in a single operation, there is required an image memory of great capacity.
(ii) Further, the scanning range of the major scanning must be as wide as the whole picture plane in the major scanning direction, and the distortion in the marginal portion wherein the scanning angle is great becomes great. It is required in the image of each picture plane of a multiformat camera for medical treatment that the distortion be small as possible, but the conventional apparatus cannot meet such requirement.
(iii) To enhance the resolving power of each divisional image, the diameter of the scanning beam must be made small, but since the scanning range is wide as described under item (ii) above, it is difficult to design a scanning optical system in which the diameter of the scanning beam is small.